Magic angle spinning spheres

In solid state NMR, samples are spun at 54.7°C cwith respect to the external magnetic field to partially average anisotropic interactions and improve spectral resolution. This is the so-called magic angle spinning (MAS). While cylindrical rotors are typically used for MAS, we have recently introduced spherical rotors towards >200kHz MAS. The current word record for MAS of cylindrical rotors is 150 kHz using 0.5 mm rotors. The difficulty in spinning faster with cylindrical rotors is there instability to the forces applied during high frequency MAS. Spherical rotors circumvent many of these problems due the inherent stability of the sphere geometry, providing an avenue for obtaining MAS frequencies >150 kHz. We have demonstrated 9.5 mm spherical rotors spinning at 10.6 kHz and 4 mm spherical rotors spinning at 28 kHz. Further scaling down to 2 mm increases the spinning frequencies to 68 kHz, which gives access to proton-detected solid-state NMR experiments. A crucial technique for biomolecular studies.

High throughput prototype production: Learning from experience.

The stator that houses the spheres utilizes a single gas stream from an aperture tangent to the stator cup. The spinning gas introduced at 35.3°C with respect to the external magnetic field orients the sphere rotating at the magic angle. 3D printing allows us to improve stator designs on a daily basis. This rapid production of new, testable prototypes, has accelerated our development of the sphere technology allowing us to rapidly scale down our rotor sizes to achieve higher spinning frequencies.